This is another of the questions that I can only suggest, not having had time and opportunity to supply experimental answer.
Do fruits contain diastase?
Two kinds of food are described by Pavy (‘Treatise on Food and Dietetics,’ page 227), in the preparation of which the conversion of starch into dextrin appears to be effected. As I have no acquaintance with these, never met with them either in Scotland or Wales, I will quote his description:
‘Sowans, seeds, or flummery, which constitutes a very popular article of diet in Scotland and South Wales, is made from the husks of the grain (oats). The husks, with the starchy particles adhering to them, are separated from the other parts of the grain and steeped in water for one or two days, until the mass ferments and becomes sourish. It is then skimmed and the liquid boiled down to the consistence of gruel. In Wales this food is called sucan. Budrum is prepared in the same manner, except that the liquid is boiled down to a sufficient consistency to form, when cold, a firm jelly. This resembles blancmange, and constitutes a light, demulcent, and nutritious article of food, which is well suited for the weak stomach.’
Here it is evident that solution takes place and a gummy substance is formed; this and the fermentation and sourish taste all indicate the action of the diastase of the seed converting the starch into dextrin and sugar, the latter passing at once into acetic fermentation. Having only just met with this passage, I am unable to supply any experimental evidence, but suggest to any of my readers who may be on the spot where either of these preparations are made, the simple experiment of adding a little diluted tincture of iodine to the sowans or budrum, preferably to the latter. If any of the starch remains as starch, a deep blue tint will be immediately struck; if this is not the case it is all converted.
I have just received a letter (while the proofs of this sheet are in course of correction) from a retired barrister in his seventy-third year, who, after a successful career in India, ‘retired in 1870 to enjoy the otium cum dig.’ Among other interesting particulars relating to animal and vegetable diet, he tells me that ‘somehow I did not, with a purely vegetable diet, excite saliva sufficient for digestion, and being constitutionally a gouty subject, I have suffered very much from gout until comparatively lately (say the last eight months), when an idea came into my head that by the use of potash I might get rid of the calcareous deposit accompanying gout, and have been taking 30 drops of liquor potassæ in my tea with very good effect. But within the last ten days, thanks to your article in “Knowledge” of January 16, 1885, I have, as it were by magic, become young again. I was not aware that the diastase of malt had the same powers as the salivary secretions. When I read your article, I commenced the experiment on my morning food, namely, oatmeal-porridge, of which for several years I have cooked daily four ounces, of which I could never eat more than half without feeling distended for an hour or two, and then again feeling hungry and a craving for more food. Since I followed your directions I have been able to eat comfortably nearly the whole (five ounces with the malt). I feel no distension for the time nor craving afterwards; I am comfortably satisfied for hours; but what is more, the diastased porridge has had the effect of removing the tendency to costiveness, which was sore trouble, and it has rendered my joints supple, and destroyed the tendency of my finger and toe-nails to grow rapidly and brittle. All this seems to have changed, as if by magic. I, therefore, write to you as a public benefactor, to thank you for your seasonable hints.’
I quote this letter (with the permission of the writer, Mr. A. T. T. Petersen) the more willingly and confidently from the fact that I have lately adopted as a regular supper diet a porridge made of oatmeal, to which about one-sixth or one-eighth of malt flour is added. I find it in every respect advantageous, far better than ordinary simple oatmeal-porridge. The following from Pavy, p. 229, indicates further the desirability of assisting the salivary glands and pancreas in digesting this otherwise excellent food. Speaking of oatmeal-porridge, he says: ‘It is apt to disagree with some dyspeptics, having a tendency to produce acidity and pyrosis, and cases have been noticed among those who have been in the daily habit of consuming it, where dyspeptic symptoms have subsided upon temporarily abandoning its use.’
My readers should try the following experiment. It supplies a striking demonstration of the potency of the diastase of malt.
Make a portion of oatmeal-porridge in the usual manner, but unusually thick—a pudding rather than a porridge; then, while it is still hot (150° or thereabouts) in the saucepan, add some dry malt flour (equal to one-eighth to one-fourth of the oatmeal used). Stir this dry flour into it and a curious transformation will take place. The dry flour instead of thickening the mixture acts like the addition of water, and converts the thick pudding into a thin porridge. I find that this paradox greatly astonishes the practical cook.